Compositions to soften fabrics and to reduce static building up in the laundering process are well known. Since the principal ingredients in commercially available fabric softeners are usually cationic in charge and since most laundry detergent products contain anionic surfactants, one must be careful in combining the two together. Thus, the softeners are usually added to the last rinse cycle of a laundry process. This is done to avoid the interaction between the cationic softener and the anionic surfactant. More recently a popular way of conditioning fabric is to impregnate sheets with the cationic surfactant and then add such sheets to moist laundry in a laundering dryer. This avoids any interaction between the cationic surfactant and the anionic surfactant.
Numerous attempts have been made to formulate laundry detergent compositions that have good cleaning properties together with textile softening properties so as to avoid the necessity of using a separate rinse-added textile softener product in addition to the usual laundry detergent. Since cleaning by definition involves the removal of material from the textile surface and textile softening normally involves deposition of material onto the same surface, these attempts have typically required a compromise in formulation between cleaning and softening performance.
Attempts to formulate aqueous heavy duty liquid laundry detergent compositions containing anionic surfactants and a quaternary ammonium fabric-softening agent like lauryl trimethyl ammonium chloride and which provide softening through the wash and static control benefits have resulted in poor physical product characteristics including phase separation or have resulted in poor fabric cleaning performance.